Wikis, I think, are mostly scary to me because I grew up during the age of Wikipedia. I remember all throughout high school people using wikipedia as a resource and I would cringe. Only one of my teachers - my favorite english teacher - mentioned that it wasn't a good thing to use because people could change it at will and it wasn't monitored all that strictly for content (so obviously, it could be inaccurate).
Then, I went to college. Being the overly academic perfectionist that I am, it was horrifying that during each of my four years, I saw someone who had written a formal research paper and cited Wikipedia. I weeped to myself at night.
For less serious things like events, maybe, I think a wiki is cool. Or having a wiki for a conference. I believe there was one for MLA last year... but for the love of all that is good and right in the world, not for a serious reference source. And if you use it as one, at least double check your information somewhere else :-/
It would be kind of nice if the library had a wiki for our programs, so people could sort of chat (possibly banter) about programs, give ideas, etc about past, present, future programs since that's such a big part of what we do here. And by programs, I mean classes and seminars and such. Haha. We could sort of facilitate it, make sure nothing crazy was going it, but for the most part let customers run the show. I think that would be a neat way of hearing what people have to say.